WASHINGTON -- A report released Tuesday by the Associated Press said that the U.S. Supreme Court may block a massive sex discrimination lawsuit against Wal-Mart on behalf of at least 500,000 women, and that could make it harder for other workers nationwide to bring class-action claims against large employers.

The 10-year-old lawsuit, argued at the Supreme Court on Tuesday, claims that Wal-Mart Stores favors men over women in pay and promotions. Billions of dollars are at stake if it is allowed to go forward as a class action suit.

In Tuesday's arguments, Justices Anthony Kennedy and Antonin Scalia suggested they were troubled by the case and lower court decisions against Wal-Mart, saying that the women’s arguments are conflicting.

Justice Ruth Bader Ginsburg said that at this stage of the lawsuit, the issue is not proving discrimination but showing enough evidence to go forward. Fellow female justices Elena Kagan and Sonia Sotomayor, along with Justice Stephen Breyer, also appeared inclined to allow the lawsuit to proceed.

The split among the justices raised the prospect of an ideologically divided ruling by the court this summer.

Business interests have lined up with Wal-Mart while civil rights, women's and consumer groups have sided with the women plaintiffs.

Both sides have painted the case as extremely consequential. The business community has said that a ruling for the women would lead to a flood of class-action lawsuits based on vague evidence. Supporters of the women say that if the court sides with Wal-Mart, it could remove a valuable weapon for combating all sorts of discrimination.

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